This project is concerned with various behavioral abnormalities resulting from hypo- and hyperthyroid states which are experimentally induced in rhesus monkeys and rats around the time of birth, and the more immediate effects of thyroid alterations in learning, memory, and motivational tasks administered to normal adult animals. Studies designed to establish rhesus monkey models of human cretinism and congenital hyperthyroidism are being pursued, with particular attention given to persisting learning deficits and how these deficits and other behavioral abnormalities, eg. hyperactivity, may be reduced by environmental stimulation. The adult-animal studies are oriented toward revealing disorders of cognitive and emotional functioning which are analogous to various psychopathological signs observed in human Graves' disease and myxedema (e.g. memory disorders, anxiety, depression). In order to elucidate further the role of thyroid hormones in both the early maturation and adult functioning of the central nervous system, this project also involves the study of metabolic and neurohistological correlates of demonstrated thyroid-behavior relationships. BIBLIOGRAPHIC REFERENCES: Davenport, J. W., Environmental therapy in hypothyroid and other disadvantaged animal populations. Chapter in R. N. Walsh and W. T. Greenough (Eds.), Environments as therapy for brain dysfunction. New York; Plenum Press, 1976, in press. Davenport, J. W., Gonzalez, L. M., Hennies, R. S., and Hagquist, W. W. Severity and timing of early thyroid deficiency as factors in the induction of learning disorders in rats. Hormones in Behavior, 1976, in press.